Objective-C 运算符

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运算符是一个符号，它告诉编译器执行特定的数学或逻辑操作。 Objective-C语言有丰富的内置运算符并提供了以下几种类型：

算术运算符
关系运算符
逻辑运算符
位运算符
赋值运算符
其他运算符

本教程将逐个讲解算术表达式，关系逻辑，按位分配和其他运算符。

算术运算符

下表列出了所有支持Objective-C语言的算术运算符。假设变量A=10，变量B=20，则：

运算符	描述	示例
+	Adds two operands	A + B will give 30
-	Subtracts second operand from the first	A - B will give -10
*	Multiplies both operands	A * B will give 200
/	Divides numerator by denominator	B / A will give 2
%	Modulus Operator and remainder of after an integer division	B % A will give 0
++	Increment operator increases integer value by one	A++ will give 11
--	Decrement operator decreases integer value by one	A-- will give 9

关系运算符

下表列出了所有支持Objective-C语言的关系运算符。假设变量A=10和变量B=20，则：

显示实例

运算符	描述	示例
==	Checks if the values of two operands are equal or not; if yes, then condition becomes true.	(A == B) is not true.
!=	Checks if the values of two operands are equal or not; if values are not equal, then condition becomes true.	(A != B) is true.
>	Checks if the value of left operand is greater than the value of right operand; if yes, then condition becomes true.	(A > B) is not true.
<	Checks if the value of left operand is less than the value of right operand; if yes, then condition becomes true.	(A < B) is true.
>=	Checks if the value of left operand is greater than or equal to the value of right operand; if yes, then condition becomes true.	(A >= B) is not true.
<=	Checks if the value of left operand is less than or equal to the value of right operand; if yes, then condition becomes true.	(A <= B) is true.

逻辑运算符

下表列出了所有支持Objective-C语言的逻辑运算符。假设变量A=1，变量B=0，那么：

显示实例

运算符	描述	示例
&&	Called Logical AND operator. If both the operands are non zero then condition becomes true.	(A && B) is false.
\|\|	Called Logical OR Operator. If any of the two operands is non zero then condition becomes true.	(A \|\| B) is true.
!	Called Logical NOT Operator. Use to reverses the logical state of its operand. If a condition is true, then Logical NOT operator will make false.	!(A && B) is true.

位运算符

位运算符位和位操作执行位。 &, |, 和 ^ 真值表如下：

p	q	p & q	p \| q	p ^ q
0	0	0	0	0
0	1	0	1	1
1	1	1	1	0
1	0	0	1	1

假设，如果A=60和B=13; 现在以二进制格式将如下：

A = 0011 1100

B = 0000 1101

-----------------

A&B = 0000 1100

A|B = 0011 1101

A^B = 0011 0001

~A = 1100 0011

下表中列出了支持Objective-C语言的位运算符。假设变量A=60和变量B=13，那么：

显示实例

运算符	描述	例子
&	Binary AND Operator copies a bit to the result if it exists in both operands.	(A & B) will give 12, which is 0000 1100
\|	Binary OR Operator copies a bit if it exists in either operand.	(A \| B) will give 61, which is 0011 1101
^	Binary XOR Operator copies the bit if it is set in one operand but not both.	(A ^ B) will give 49, which is 0011 0001
~	Binary Ones Complement Operator is unary and has the effect of 'flipping' bits.	(~A ) will give -61, which is 1100 0011 in 2's complement form.
<<	Binary Left Shift Operator. The left operands value is moved left by the number of bits specified by the right operand.	A << 2 will give 240, which is 1111 0000
>>	Binary Right Shift Operator. The left operands value is moved right by the number of bits specified by the right operand.	A >> 2 will give 15, which is 0000 1111

赋值运算符

支持Objective-C语言的赋值运算符有以下：

显示例子

运算符	描述	示例
=	Simple assignment operator, Assigns values from right side operands to left side operand	C = A + B will assign value of A + B into C
+=	Add AND assignment operator, It adds right operand to the left operand and assigns the result to left operand	C += A is equivalent to C = C + A
-=	Subtract AND assignment operator, It subtracts right operand from the left operand and assigns the result to left operand	C -= A is equivalent to C = C - A
*=	Multiply AND assignment operator, It multiplies right operand with the left operand and assigns the result to left operand	C = A is equivalent to C = C A
/=	Divide AND assignment operator, It divides left operand with the right operand and assigns the result to left operand	C /= A is equivalent to C = C / A
%=	Modulus AND assignment operator, It takes modulus using two operands and assigns the result to left operand	C %= A is equivalent to C = C % A
<<=	Left shift AND assignment operator	C <<= 2 is same as C = C << 2
>>=	Right shift AND assignment operator	C >>= 2 is same as C = C >> 2
&=	Bitwise AND assignment operator	C &= 2 is same as C = C & 2
^=	bitwise exclusive OR and assignment operator	C ^= 2 is same as C = C ^ 2
\|=	bitwise inclusive OR and assignment operator	C \|= 2 is same as C = C \| 2

其他运算符 ↦ sizeof & 三元

一些其他重要的运算符，包括sizeof 和 ? :支持Objective-C语言。

显示示例

运算符	描述	例子
sizeof()	Returns the size of an variable.	sizeof(a), where a is integer, will return 4.
&	Returns the address of an variable.	&a; will give actual address of the variable.
*	Yiibaier to a variable.	*a; will yiibaier to a variable.
? :	Conditional Expression	If Condition is true ? Then value X : Otherwise value Y

Objective-C中的运算符优先级

运算符优先级确定在表达式中的分组。这会影响如何计算一个表达式。某些运算符有比别人更高的优先级，例如，乘法运算符的优先级高于加法运算符：

例如，X=7+3* 2;这里，x是分配13，不是20，因为运算符*的优先级高于+，所以它首先被乘以3 * 2，然后加7。

在这里，运算符具有最高优先级，出现在上面的表中，那些与最低的出现在底部。在一个表达式中，优先级较高的运算符将首先计算。

类别	运算符	关联性
Postfix	() [] -> . ++ - -	Left to right
Unary	+ - ! ~ ++ - - (type)* & sizeof	Right to left
Multiplicative	* / %	Left to right
Additive	+ -	Left to right
Shift	<< >>	Left to right
Relational	< <= > >=	Left to right
Equality	== !=	Left to right
Bitwise AND	&	Left to right
Bitwise XOR	^	Left to right
Bitwise OR	\|	Left to right
Logical AND	&&	Left to right
Logical OR	\|\|	Left to right
Conditional	?:	Right to left
Assignment	= += -= *= /= %=>>= <<= &= ^= \|=	Right to left
Comma	,	Left to right

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